C. GENERAL PHYSICS. 179 



THE DISCHARGE OP ELECTRIFIED CONDUCTORS. 



ITclmholtz, after explaining certain phenomena observed 

 by Kiess, states that their explanation is easy to understand, 

 provided the discharge of a battery be not represented as a 

 simple movement of electricity in one direction, but as a se- 

 ries of oscillations between the two coatings oscillations 

 which become less and less continually until the vis viva is 

 extinguished by the sum of the resistance. But Montier, by 

 a critical comparison of the works of Helmholtz and Clausius, 

 shows that the discharge may be equally well represented by 

 a movement of the electricity directed from one coating to- 

 ward the other. Lonely Edin., and Dub. Phil. 3Iay., XLVII., 

 157. 



THE IMPERMEABILITY OF A NON-HOMOGENEOUS ATMOSFIIERE 



TO SONOROUS VIBRATIONS. 



Professor Tyndall has experimentally shown that sound 

 can not be transmitted through a column of gas of alternate 

 dense and rarefied layers, formed by allowing sheets of coal 

 gas to ascend between descending currents of carbonic gas,. 

 He sounded a bell at one end of a loner box containing 

 these columns of gas, and observed that a sensitive flame 

 placed at the other end of the box remained motionless; but 

 if the gases were replaced by air, or any gas of uniform den- 

 sity, the flame was depressed at each tap on the bell. The 

 same effects were obtained when the box contained vertical 

 columns of hot and cold air. Proc. Roy. 80c. , February, 187 4. 



ON THE REFLECTION OF SOUND FROM FLAMES AND HEATED 



GASES. 



In the following experiments, Professor A. M. Mayer has 

 shown in a simple and striking manner the reflection of sound 

 by sheets of flame and heated gases, and has even obtained 

 approximate measures of these reflecting powers: Take two 

 similar resonators, and place the planes of their mouths at 

 a right angle ; then in this angle firmly fix the tuning-fork 

 corresponding to the resonators, so that the broad face of 

 one of its prongs faces the mouth of one resonator, while the 

 space between the prongs faces the mouth of the other reso- 

 nator. By trial, these two planes of the fork are placed at 



